1. Field of the Invention
The invention relates to insulated conductors for transformer windings and other inductive apparatus, and more particularly to such insulated conductors in which an insulator is provided between the flat sides of two conductor strands to form a glued joint therebetween with insulator spacers to maintain the conductors in spaced relationship to one another.
2. Prior Art
Upon a short-circuit in transformers, there arise forces in the windings which lead to the winding breaking, if it is not sufficiently resistive or well supported.
One way of increasing the breaking strength of a winding and therefore the resistance to short-circuit forces is to increase the thickness of the conductor which, with surrounding insulation, is used for building up the winding. Increasing the thickness of the conductor, however, results in increased additional losses and in possible problems of locally high temperatures in the winding. Additionally, the winding becomes electrically over-dimensioned and more space-demanding.
It is known to reduce the additional losses by using continuously transposed conductors when constructing transformer windings. Such conductors are built up of several varnished conductor strands having substantially rectangular shape, which within a common surrounding insulation, usually in the form of a paper wrapping, are arranged in parallel in at least two rows. Within each row one conductor strand may be arranged with a flat side facing a flat side of an adjacent conductor strand. Each varnished conductor strand may be provided with a coating of a resin, which is uncured or semi-cured so that the conductor strands are movable with respect to each other when building up a winding. The uncured or semi-cured resin is cured only when the winding has been given its final shape, usually in connection with the drying of the winding. Because of the plurality of the conductor strands and the thickness of the conductor, the conductor is difficult to wind and not possible to use for complicated windings, such as interleaved disc windings, because of the necessary transitions between one disc and an adjacent disc in such windings. Continuously transposed conductors are therefore normally used only for windings consisting of a relatively small number of turns of the conductor arranged in a layer on an insulating cylinder, and particularly for regulating windings.